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Additions & Extensions

Home Addition in Ontario

A home addition adds finished floor area to your house — a family room off the back, a larger kitchen, an extra bedroom wing, or a full second-floor top-up. In Ontario, every addition needs a building permit, so the project really starts on paper: measured drawings of the existing house, a design that works with your lot, and a permit set your municipal building department will accept. From there the build follows a predictable sequence — excavation, footings, framing, envelope, services, and finishing.

Zoning shapes what you can build before structure ever comes up. Setbacks, lot coverage, and height limits differ from one municipality to the next, and many urban lots need a minor variance from the committee of adjustment before a permit can be issued. A contractor who scopes the zoning picture early saves you months. Once approved, new foundations go on footings below frost depth, the new framing ties into the existing structure, and inspections happen at set stages through the build.

What this covers

  • Site measure and as-built drawings of the existing house
  • Design and permit drawings prepared for municipal submission
  • Zoning review, with minor variance support where the lot needs it
  • Excavation and concrete footings below frost depth
  • Foundation, framing, and structural tie-in to the existing house
  • Roofing, windows, insulation, and exterior cladding to match
  • Electrical, plumbing, and HVAC extensions by licensed trades
  • Drywall, flooring, trim, and interior finishing

What affects the price

  • Footprint and number of storeys being added
  • Foundation type — full basement, crawl space, or slab
  • How much of the existing structure needs reinforcement at the tie-in
  • Whether a minor variance is needed, which adds time and fees
  • Matching existing brick, siding, and rooflines versus a contrasting design
  • Level of interior finish, from basic drywall to full kitchen or bathroom fit-outs

Every home is different, so we don’t publish flat prices — the quote is free and based on your actual job.

Home Addition near you

We take quote requests across Ontario. Local pages:

TorontoOttawaMississaugaBramptonCaledonHamiltonVaughanMarkhamRichmond HillAuroraNewmarketGeorginaWhitchurch-StouffvilleKingOakvilleBurlingtonMiltonHalton HillsOshawaWhitbyAjaxPickeringClaringtonKitchenerWaterlooCambridgeLondonBarrieInnisfilBradford West GwillimburyCollingwoodSt. CatharinesNiagara FallsWellandGrimsbyFort ErieGuelphWindsorKingstonGreater SudburyPeterboroughThunder BayBrantfordBellevilleSarniaWoodstockStratfordOrangevilleCornwallNorth BaySault Ste. MarieChatham-KentOrilliaWasaga BeachMidlandNew TecumsethSt. ThomasKawartha LakesCobourgPort HopePrince Edward CountyQuinte WestLeamingtonOwen SoundBracebridgeHuntsvilleNiagara-on-the-LakeTimminsBrockville

Common questions

Do I always need a building permit for an addition?
Yes. Any addition that adds floor area or alters structure requires a building permit under the Ontario Building Code, no matter the size. Building without one risks stop-work orders, forced removal, and problems when you sell. The permit process also brings staged inspections — footings, framing, insulation — which protect you as much as they satisfy the municipality.
What is a minor variance and will I need one?
Zoning bylaws set limits on setbacks, lot coverage, and height. If your design pushes past any of them, you apply to the committee of adjustment for a minor variance — a public hearing where neighbours can comment. Many additions on narrow urban lots need one. It typically adds two to four months, so it should be identified during design, not after.
How long does a home addition take?
Design and permits commonly run three to six months, longer with a variance. Construction on a typical single-storey addition runs roughly three to five months from excavation to finished interior, and two-storey projects take longer. Weather, inspection scheduling, and material lead times all move the timeline, which is why a realistic schedule belongs in your quote.
Can we live in the house during construction?
Usually, yes. Most additions are built as a closed shell before the wall between old and new is opened, which keeps dust and weather out of the main house for much of the build. Expect disruption during the tie-in, service connections, and any work that touches your existing kitchen or bathrooms. Your contractor should sequence the messy stages and tell you when they land.

Ready to sort out your home addition?

Tell us what you're planning — one room or the whole home — and get a free quote.

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